The question of whether future broadband networks will be composed of circuit switches with independent networks of packet switches, or circuit switches with packet channel emulation or vise versa, has been controversial (see, e.g., L.T. Wu, S.H. Lee, and T.T. Lee, "Dynamic TDM--A Packet Approach to Broadband Networking", in IEEE Int. Conference on Communications, Seattle, Washington, 1987; L.T. Wu, E. Arthurs, and W.D. Sincoski, "A Packet Network for BISDN Applications", in B. Platner and P. Gunzburger, editors, Proc. of 1988 Zurich Seminar on Digital Commun., pages 191-197, Zurich, 1988; Peter O'Reilly, "Implication of Very Wide Fiber Bandwidth for Network Architecture", Fiber and Integrated Optics, 7:159-171, 1988). The widespread use of optical fibers in the public network has made equally controversial the question of whether the switches will be non-blocking electronic designs with fixed internal channel bandwidth linking demultiplexed optical input channels (see, e.g., Y.N. Hui and E. Arthurs, "A Broadband Packet Switch for Multirate Services", in IEEE International Conference on Communications, Seattle, Washington, 1987) or hybrid electronic/optical designs (see, e.g., E. Arthurs, M.S. Goodman, H. Kobrinski, and M.P. Vecchi, "HYPASS: An Optoelectronic Hybrid Packet-Switching System", J. on Selected Areas Commun., 6:1500-1510,1988) or even all optically controlled switches.
These questions have been exacerbated by the rapid developments in electro-optic device technology, which is producing better lasers whose modulation rates are continually increasing. Recent experiments have demonstrated the potential of individual laser modulation rates in excess of 10 Gbits/sec. Furthermore, experiments using multiwavelength technology have demostrated a data transmission rate of more than 36 Gbits/sec for point-to-point links over an individual single-mode optical fiber using eighteen separate single wavelength channels, each modulated at 2 Gbits (see, e.g., M.P. Vecchi, R.M. Bulley, M.S. Goodman, H. Kobrinski, and C.A. Brackett, "High-bit-rate Measurements in the LAMBDANET Multiwavelength Optical Star Network", in Optical Fiber Commun. Conf., WO2, page 95, New Orleans, LA, January 1988; see, also, H. Kobrinski, R.M. Bulley, M.S. Goodman, M.P. Vecchi, C.A. Brackett, L. Curtis, and J.L. Gimlett, "Demostration of High Capacity in the LAMBDANET Architecture: A Multiwavelength Optical Network", Electron. Lett., 23:824,1987).
There is also the question as to whether network switching elements should incorporate only unicast traffic or whether broadcast traffic (e.g., one-to-many video switching) or multicast traffic (e.g. selective broadcast) should be integrated as well. While some electronic network switches (see, e.g., T.T. Lee, R. Boorstyn, and E. Arthurs, "The Architecture of a Multicast Broadband Packet Switch", Proc. of INFOCOM'88, page 1, 1988; T.T. Lee, "Nonblocking Copy Networks for Multicast Packet Switching," Proc. Int. Zurich Seminar on Digital Communications, pages 221-229,1988) have incorporated a multicast capability, previous multiwavelength optical switch designs (see, e.g., E. Arthurs, M.S. Goodman, H. Kobrinski, and M.P. Vecchi, "HYPASS: An Optoelectronic Hybrid Packet-Switching System," J. on Selected Areas Commun, 6:1500-1510, 1988; K.Y. Eng, "A Photonic Knockout Switch For High Speed Packet Networks", in IEEE/IEICE Global Telecomm. Conf., pages 47.2.1-47.2.5, Tokoyo, December, 1987; A.S. Acampora, M.J. Karol, and M.G. Hluchyj, "Multihop Lightwave Networks: A New Approach to Achieve Terabit Capabilities", Proc. ICC'88, 1:1478-1484,1988) have not satisfactorily incorporated multicast capability.
In view of the above, it is an object of the present invention to provide a broadband optical switch with a throughput in the many Gbits/sec range and with multicast switching capabilities. The primary intended applications for the inventive switch are in the public network and for LAN/MAN bridging, although other applications such as packet concentration/multiplexing are possible as well. It is a further object of the invention to provide an optical switch design which can support both prioritized demand access traffic and reserved traffic, as well as provide unicast and multicast switching in a unified framework.